Solar cell, method of manufacturing the same, and photovoltaic module

Abstract

This application provides a solar cell, its fabrication method, and a photovoltaic module. The fabrication method of the solar cell includes: providing a substrate; forming a first composite layer on the back side; forming borosilicate glass on the side of the first composite layer away from the substrate; removing a portion of the borosilicate glass and a portion of the P-type doped polycrystalline silicon layer; doping the exposed P-type doped polycrystalline silicon layer to form an N-type doped polycrystalline silicon layer; etching a portion of the back side of the pre-cell structure; texturing the front side of the pre-cell structure, and forming a passivation layer and an anti-reflection layer on the front and back sides of the etched structure; forming an electrode on the back side of the pre-cell structure to form a solar cell. This application simplifies the process and reduces manufacturing costs by partially removing the borosilicate glass and compensating for the inversion of the exposed p-poly to form n-poly, thereby eliminating the step of depositing a second poly layer.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and more specifically, to a solar cell, its preparation method, and a photovoltaic module. Background Technology

[0002] TBC (Tunneled Oxide Passivated Contact) battery technology combines TBC with Interdigitated Back Contact (IBC) technology. TBC batteries utilize phosphorus-doped polycrystalline silicon (n-poly) or boron-doped polycrystalline silicon (p-poly) with a tunneling passivation dielectric layer to form a fully passivated back contact structure. Compared to traditional IBC batteries, the fully passivated contact structure significantly improves passivation performance and efficiency. However, the n-poly and p-poly layers in the above fabrication process require two fabrication steps, leading to the following problems: Double poly deposition requires additional production equipment, increasing investment costs; after the second poly deposition, the overall poly film thickness is thicker (over 300nm), resulting in greater silicon wafer deformation and more fragmentation under stress; the second poly deposition requires a larger laser patterning area, resulting in lower yield and greater damage. Summary of the Invention

[0003] This application provides a solar cell, its preparation method, and a photovoltaic module to solve the problem in related technologies where the n / p-poly film is prepared using two preparation processes, resulting in a thicker overall poly film and lower production capacity.

[0004] According to one aspect of this application, a method for fabricating a solar cell is provided, comprising: providing a substrate having a front side and a back side; forming a first composite layer on the back side, the first composite layer including a tunneling passivation layer and a P-type doped polycrystalline silicon layer; forming borosilicate glass on a side of the first composite layer opposite to the substrate; removing a portion of the borosilicate glass and a portion of the P-type doped polycrystalline silicon layer, exposing a portion of the P-type doped polycrystalline silicon layer; doping the exposed P-type doped polycrystalline silicon layer to form an N-type doped polycrystalline silicon layer, thereby forming a preliminary cell structure; and etching the back side of the preliminary cell structure to expose the N-type doped polycrystalline silicon layer. The N-type doped polycrystalline silicon layer is spaced apart from the P-type doped polycrystalline silicon layer, and the back side of the substrate has an exposed area. The front side of the pre-cell structure is texturized, and a passivation layer and an anti-reflection layer are formed on the front and back sides of the structure after the etching process. The passivation layer on the back side of the pre-cell structure covers the P-type doped polycrystalline silicon layer, the exposed area, and the N-type doped polycrystalline silicon layer. An electrode is formed on the back side of the pre-cell structure. The electrode penetrates the passivation layer and the anti-reflection layer and contacts the P-type doped polycrystalline silicon layer or the N-type doped polycrystalline silicon layer to form the solar cell.

[0005] Optionally, during the formation of the pre-cell structure, and after the formation of the N-type doped polycrystalline silicon layer, the fabrication method further includes: forming a phosphosilicate glass on the side of the N-type doped polycrystalline silicon layer away from the substrate.

[0006] Optionally, the step of forming the first composite layer includes: alternately forming the tunneling passivation layer and the P-type doped polysilicon layer on the back side of the substrate.

[0007] Optionally, the step of forming the N-type doped polysilicon layer includes: doping the first composite layer to form alternating tunneling passivation layers and N-type doped polysilicon layers.

[0008] Optionally, before the step of forming a passivation layer and an antireflection layer on the front and back sides of the structure after the etching process of the pre-cell structure, the preparation method further includes: removing the borosilicate glass and the phosphosilicate glass.

[0009] Optionally, the thickness of the exposed P-type doped polysilicon layer is 2 / 5 to 4 / 5 of the thickness of the unexposed P-type doped polysilicon layer.

[0010] According to another aspect of this application, a solar cell is provided, comprising: a pre-cell structure including: a substrate, a first composite layer, borosilicate glass, and an N-type doped polycrystalline silicon layer, wherein: the substrate includes a front side and a back side, the first composite layer is located on the back side of the substrate, the first composite layer includes a tunneling passivation layer and a P-type doped polycrystalline silicon layer, the P-type doped polycrystalline silicon layer is located on a portion of the surface of the tunneling passivation layer facing away from the substrate, the borosilicate glass is located on the side of the P-type doped polycrystalline silicon layer facing away from the substrate, and the N-type doped polycrystalline silicon layer is located on the side of the P-type doped polycrystalline silicon layer facing away from the substrate. The tunneling passivation layer is located on a portion of the surface opposite to the substrate; a passivation layer is located on the front and back sides of the pre-cell structure, with the passivation layer on the back side covering the P-type doped polycrystalline silicon layer, a portion of the substrate, and the N-type doped polycrystalline silicon layer; an anti-reflection layer is located on the front and back sides of the pre-cell structure, and the anti-reflection layer covers the passivation layer; an electrode is located on the back side of the pre-cell structure, and the electrode penetrates the passivation layer and the anti-reflection layer to contact the P-type doped polycrystalline silicon layer or the N-type doped polycrystalline silicon layer to form the solar cell.

[0011] Optionally, the thickness of the N-type doped polysilicon layer is 2 / 5 to 4 / 5 of the thickness of the P-type doped polysilicon layer.

[0012] Optionally, the doping concentration of the N-type doped polysilicon layer is 2E20cm⁻¹. -3 ~1E21cm -3 .

[0013] According to another aspect of this application, a photovoltaic module is provided, comprising at least one of the aforementioned solar cells.

[0014] This application provides a method for fabricating a solar cell. First, a substrate with a front and a back side is provided. Then, a tunneling passivation layer, a P-type doped polycrystalline silicon layer, and borosilicate glass are formed on the back side. Part of the borosilicate glass and part of the P-type doped polycrystalline silicon layer are removed, exposing a portion of the P-type doped polycrystalline silicon layer. The exposed P-type doped polycrystalline silicon layer is then inverted to form an N-type doped polycrystalline silicon layer, thus forming a preliminary cell structure. The back side of the preliminary cell structure is etched to separate the N-type doped polycrystalline silicon layer from the P-type doped polycrystalline silicon layer, resulting in an exposed area on the back side of the substrate. This single-step fabrication process obtains both the P-type and N-type doped polycrystalline silicon layers, reducing the overall poly layer thickness and the area requiring localized opening of the borosilicate glass film. This increases the fabrication capacity of the solar cell and reduces manufacturing costs. It solves the problem in related technologies where a two-step fabrication process for n / p-poly results in a thicker overall poly film and lower production capacity. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0016] Figure 1 This is a flowchart illustrating a method for fabricating a solar cell according to an embodiment of this application;

[0017] Figure 2 This is a schematic cross-sectional view of the substrate after providing a substrate in a method for fabricating a solar cell according to an embodiment of this application.

[0018] Figure 3 Is Figure 2 A schematic diagram of the cross-sectional structure of the substrate after the first composite layer is fabricated on the substrate provided in the image;

[0019] Figure 4 Yes Figure 3 A schematic diagram of the cross-sectional structure of the substrate after the partial removal of the borosilicate glass and the P-type doped polycrystalline silicon layer formed in the process;

[0020] Figure 5 Is Figure 4 A schematic diagram of the cross-sectional structure of the substrate for preparing the cell after inverting the exposed P-type doped polycrystalline silicon layer to form an N-type doped polycrystalline silicon layer and forming phosphosilicate glass on the N-type doped polycrystalline silicon layer.

[0021] Figure 6 Is Figure 5 A schematic diagram of the cross-sectional structure of the substrate after texturing one side of the pre-formed battery structure and etching the other side.

[0022] Figure 7 Is Figure 6 A passivation layer and an anti-reflection layer are formed on the texturing surface of the pre-cell structure after etching. A cross-sectional view of the substrate after the passivation layer and anti-reflection layer are formed on the etched surface.

[0023] Figure 8 Is Figure 7 A schematic diagram of the cross-sectional structure of the substrate after the electrode is fabricated on the pre-cell structure obtained in the process.

[0024] The above figures include the following reference numerals:

[0025] 10. Substrate; 20. First composite layer; 30. Tunneling passivation layer; 40. P-type doped polysilicon layer; 50. Borosilicate glass; 60. N-type doped polysilicon layer; 70. Passivation layer; 80. Antireflection layer; 90. Electrode; 100. Phosphosilicate glass. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0028] It should be noted that the terms "second," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] In related technologies, the n-poly and p-poly structures on the back of TBC batteries are formed by two separate depositions. Due to the two poly depositions, additional production equipment is required, which increases the production investment cost. Moreover, after the second poly deposition, the overall thickness of the poly film is thicker (above 300nm), which leads to greater deformation and more fragmentation of the silicon wafer under stress. In addition, the second poly deposition results in a larger laser patterning area, lower production capacity, and greater damage.

[0030] Therefore, in order to address the above problems, this application provides a method for preparing a solar cell, such as... Figure 1 As shown, the method for fabricating this solar cell includes:

[0031] S1 provides a substrate having a front side and a back side;

[0032] S2, a first composite layer is formed on the back side, the first composite layer including a tunneling passivation layer and a P-type doped polysilicon layer;

[0033] S3, borosilicate glass is formed on the side of the first composite layer away from the substrate;

[0034] S4, remove part of the borosilicate glass and part of the P-type doped polysilicon layer, so that part of the P-type doped polysilicon layer is exposed;

[0035] S5, doping the exposed P-type doped polycrystalline silicon layer to form an N-type doped polycrystalline silicon layer, thus forming the preliminary cell structure;

[0036] S6, the back side of a portion of the pre-built cell structure is etched to separate the N-type doped polysilicon layer from the P-type doped polysilicon layer, and the back side of the substrate has an exposed area.

[0037] S7, texturing is performed on the front side of the pre-cell structure, and passivation and anti-reflection layers are formed on the front and back sides of the structure after etching. The passivation layer on the back side of the pre-cell structure covers the P-type doped polysilicon layer, the exposed area and the N-type doped polysilicon layer.

[0038] S8, an electrode is formed on the back of the pre-built cell structure. The electrode penetrates the passivation layer and the anti-reflection layer and contacts the P-type doped polycrystalline silicon layer or the N-type doped polycrystalline silicon layer to form a solar cell.

[0039] In the fabrication of solar cells, to avoid localized efficiency degradation, a two-stage deposition process is typically used to separately prepare n / p-poly layers. First, a p-poly layer is formed on the back of the silicon wafer. Then, the p-poly layer in the area where n-poly is to be formed is laser-etched. This etched area is relatively large. N-poly is then deposited in this etched area. During the formation of n-poly, some of it may cover the p-poly layer. This covered portion of the n-poly is then removed. Finally, the area where n-poly and p-poly meet is etched again to isolate them. However, solar cells fabricated using this two-stage poly deposition process suffer from problems such as a thicker overall poly layer, a larger laser-etched area, lower production capacity, and greater laser damage, resulting in increased manufacturing costs.

[0040] This application provides a method for fabricating a solar cell. First, a first composite layer, including a tunneling passivation layer and a P-type doped polycrystalline silicon layer, is formed on a substrate having a front and a back side. Then, borosilicate glass is formed on the side of the first composite layer facing away from the substrate, and a portion of the borosilicate glass and a portion of the P-type doped polycrystalline silicon layer are removed, exposing a portion of the P-type doped polycrystalline silicon layer. Next, the exposed P-type doped polycrystalline silicon layer is doped to form an N-type doped polycrystalline silicon layer, forming an n-poly structure. Subsequently, the back side is etched to separate the N-type doped polycrystalline silicon layer from the P-type doped polycrystalline silicon layer, forming a preliminary cell structure. The front side is texturized, and passivation layers and anti-reflection layers are formed on both the front and back sides of the structure to form the solar cell. This application utilizes a partial film-opening + wet cleaning method to achieve the formation of an n-poly structure on a silicon wafer, thereby improving cell efficiency and production capacity. By eliminating the secondary poly fabrication, equipment investment and silicon wafer stress deformation are reduced, while laser damage is reduced and laser production capacity is increased. This improves cell efficiency while reducing manufacturing costs and technical difficulty.

[0041] Exemplary embodiments of the method for fabricating a solar cell according to this application will now be described in more detail. However, these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that the disclosure of this application is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art.

[0042] First, such as Figure 2 As shown, the above step S1 is performed: a substrate 10 is provided, which has a front side and a back side.

[0043] In step S1 above, the material of the substrate 10 can be one or more of silicon or silicon carbide monocrystalline silicon, polycrystalline silicon or amorphous silicon, but is not limited to the above types. Those skilled in the art can also make reasonable selections of the substrate material according to actual needs.

[0044] After the step of providing the substrate in step S1 above, as follows Figure 3 As shown, the above step S2 is performed: a first composite layer 20 is formed on the back side, the first composite layer 20 including a tunneling passivation layer 30 and a P-type doped polysilicon layer 40.

[0045] Specifically, the material of the tunneling passivation layer 30 can be any one of silicon oxide, silicon nitride, and aluminum oxide, or a multilayer composite film, specifically SiO2, with a thickness of 1.3–2.5 nm. The aforementioned P-type doped polysilicon layer 40 is a polysilicon layer in which P-type doping is achieved by introducing P-type dopant ions (such as boron ions) into the polysilicon, with a thickness of 100–400 nm.

[0046] Specifically, after polishing the substrate 10, a tunneling passivation layer 30 and a P-type doped polycrystalline silicon layer 40 are prepared. The tunneling passivation layer 30 can effectively reduce the surface recombination rate of electrons and holes and improve the charge separation efficiency, thereby improving the photoelectric conversion efficiency of the photovoltaic cell. The P-type doped polycrystalline silicon layer 40 can improve the conductivity of the cell, reduce resistance loss, and further improve the output power of the photovoltaic cell.

[0047] In some alternative implementations, such as Figure 3 As shown, the steps for forming the first composite layer include: alternately forming a tunneling passivation layer 30 and a P-type doped polysilicon layer 40 on the back side of the substrate.

[0048] In the above optional implementations, such as Figure 3 As shown, by repeatedly performing the process of forming a tunneling passivation layer 30 and a P-type doped polycrystalline silicon layer 40, the tunneling passivation layer 30 and the P-type doped polycrystalline silicon layer 40 are alternately formed on the back side until the required thickness and structure are achieved. This can effectively improve the performance of solar cells, increase their photoelectric conversion efficiency, and also improve the stability and durability of the cells.

[0049] The thickness of the borosilicate glass and the P-type doped polycrystalline silicon layer can be adjusted. The film formed by the P-type doped polycrystalline silicon layer and the borosilicate glass can also be a stacked structure of alternating SiO2 / p-poly / SiO2 / p-poly.

[0050] After the step of forming the first composite layer in step S2 above, as Figure 3 As shown, the above step S3 is performed: borosilicate glass 50 is formed on the side of the first composite layer 20 away from the substrate.

[0051] The aforementioned borosilicate glass (BSG) is a special glass material mainly composed of boron, silicon, and other oxides. It has a thickness of 40–150 nm, excellent light transmittance and high temperature resistance, and can effectively protect the photoelectric components inside the solar panel. In addition, it also has good mechanical strength and chemical stability, which can ensure the long-term stable operation of the solar cell. Figure 3 Substrate 10 in Figure 2 The description is consistent with that in the text.

[0052] After the step of forming borosilicate glass in step S3 above, as follows Figure 4 As shown, the above step S4 is performed: part of the borosilicate glass 50 and part of the P-type doped polycrystalline silicon layer 40 are removed, so that part of the P-type doped polycrystalline silicon layer 40 is exposed.

[0053] Specifically, laser ablation is used to remove part of the borosilicate glass 50 (BSG). Laser irradiation can quickly and accurately remove the borosilicate glass 50. The thickness of the BSG in the area not laser ablation is 35-140 nm, thereby effectively exposing the P-type doped polycrystalline silicon layer 40. Wet etching is then used to remove part of the P-type doped polycrystalline silicon layer 40. Wet etching can further clean the ablation cross-section of the borosilicate glass 50, removing any residual contaminants and impurities, ensuring the purity and quality of the silicon layer, and ensuring the quality and stability of the doped silicon layer, thereby improving the photoelectric conversion efficiency of the battery.

[0054] In the region where the laser-coated layer is not exposed, the relatively thick BSG effectively blocks the diffusion of N-type doped ions when the exposed P-type doped polycrystalline silicon layer is inverted to form an N-type doped polycrystalline silicon layer. The N-type doped ions can be phosphorus atoms, thus protecting the P-type doped polycrystalline silicon under the BSG from phosphorus doping. This allows the solar cell to have both P-type and N-type doped polycrystalline silicon in the same layer, reducing the thickness of the solar cell. Figure 4 The substrate 10 and the tunnel passivation layer 30 in Figure 3 The description is consistent with that in the text.

[0055] After the step S4 above, which exposes part of the P-type doped polysilicon layer, as follows: Figure 5 As shown, step S5 is performed: the exposed P-type doped polycrystalline silicon layer 40 is doped to form an N-type doped polycrystalline silicon layer 60, thus forming a preliminary cell structure.

[0056] Specifically, N-type impurities are introduced into the P-type doped polycrystalline silicon layer 40 to change its conductivity, forming an N-type doped polycrystalline silicon layer 60. A phosphorus-containing dopant can be used to heavily dope the laser-opened region to compensate for boron in the P-type doped polycrystalline silicon layer, thus inverting to form the N-type doped polycrystalline silicon layer. After forming the N-type doped polycrystalline silicon layer, a phosphosilicate glass 100 is prepared on it through deposition or oxidation processes. The aforementioned N-type impurities are elements from Group V, such as phosphorus, nitrogen, arsenic, and bismuth. Figure 5 The description of the substrate 10, tunneling passivation layer 30 and borosilicate glass 50 is consistent with... Figure 4 Consistent with the above.

[0057] The phosphorus doping described above can be achieved through one or more of the following methods: high-temperature thermal diffusion of POCl3, ion implantation, ion beam epitaxy, and molecular beam epitaxy. However, it is not limited to these methods, and those skilled in the art can select the appropriate phosphorus doping method according to actual needs. The aforementioned N-type doped polycrystalline silicon layer plays a role in transporting and concentrating negative charges, thereby forming current. Its doping concentration and thickness affect the performance of the battery; a high doping concentration and appropriate thickness can improve the battery efficiency.

[0058] In some alternative embodiments, the step of forming an N-type doped polysilicon layer further includes: doping the first composite layer to form alternating tunneling passivation layers and N-type doped polysilicon layers.

[0059] In the above optional embodiments, it can be achieved by ion implantation technology or chemical vapor deposition technology. Ion implantation technology can be used to introduce the material to be doped (such as phosphorus, nitrogen, arsenic and bismuth) into the first composite layer by ion implantation. During the implantation process, the implantation energy and dosage are controlled to ensure the required doping concentration and distribution. Alternatively, chemical vapor deposition technology can be used to introduce doping gas in an appropriate step during the preparation of the first composite layer, so that the doped atoms can be uniformly distributed in the composite layer to form a tunneling passivation layer and an N-type doped polycrystalline silicon layer.

[0060] The thickness of the aforementioned N-type doped polycrystalline silicon layer and phosphosilicate glass can be adjusted. The film composed of the N-type doped polycrystalline silicon layer and phosphosilicate glass can also be a SiO2 / n-poly / SiO2 / n-poly stacked structure film. Local laser ablation is performed on the outermost SiO2 (borosilicate glass) layer of the SiO2 / p-poly / SiO2 / p-poly stacked structure, and the exposed P-type doped polycrystalline silicon layer is implanted with inversion ions. N-type ions will diffuse downward layer by layer, eventually forming a SiO2 / n-poly / SiO2 / n-poly stacked structure film.

[0061] In some alternative embodiments, during the formation of the pre-cell structure, and after the formation of the N-type doped polycrystalline silicon layer, the fabrication method further includes forming a phosphosilicate glass 100 (PSG) on the side of the N-type doped polycrystalline silicon layer facing away from the substrate.

[0062] The aforementioned Phosphosilicate Glass 100 (PSG) is a special glass material composed of phosphate and silicon dioxide. It has good optical properties and chemical stability, as well as a low coefficient of thermal expansion and good thermal conductivity, making it suitable for applications in high-temperature environments.

[0063] Specifically, the side of the N-type doped polycrystalline silicon layer facing away from the substrate is cleaned and treated to ensure that the surface is clean and dust-free. The substrate is then placed in a PECVD (plasma-enhanced chemical vapor deposition) device, and a phosphosilicate glass film is deposited on the surface by chemical vapor deposition. During the deposition process, the properties and thickness of the PSG film are controlled by adjusting parameters such as deposition temperature, pressure, and gas flow rate. After the PSG deposition is completed, heat treatment is usually required to improve the density and stability of the PSG film.

[0064] After the step of forming the preliminary battery structure in step S5 above, as follows Figure 6 As shown, step S6 is performed: the back side of a portion of the prepared cell structure is etched to separate the N-type doped polysilicon layer 60 from the P-type doped polysilicon layer 40, and the back side of the substrate 10 has an exposed area. Figure 6 The tunneling passivation layer 30 and Figure 3 The description is consistent with that in the text.

[0065] In some alternative embodiments, the preparation method further includes removing borosilicate glass and phosphosilicate glass.

[0066] The removal methods described above can be selected from one or more of the following: corrosion using chemical solutions or acid / alkali solutions, mechanical scraping, high-temperature grinding, and hot pressing. However, they are not limited to these methods. Those skilled in the art can also make reasonable selections of removal methods according to actual needs.

[0067] Specifically, on the back of the prepared battery structure, an etching process is used to remove borosilicate glass, phosphosilicate glass, a portion of the N-type doped polycrystalline silicon layer, and a portion of the P-type doped polycrystalline silicon layer. The etching process for removing the borosilicate glass and phosphosilicate glass can be a wet etching process or a dry etching process. The process for removing the portion of the N-type doped polycrystalline silicon layer and the portion of the P-type doped polycrystalline silicon layer can be an exposure and development process or a laser film-opening process. For example, by irradiating the material surface with a laser beam, the portion of the N-type doped polycrystalline silicon layer and the portion of the P-type doped polycrystalline silicon layer can be rapidly evaporated or burned off, thereby separating the N-type doped polycrystalline silicon layer from the P-type doped polycrystalline silicon layer.

[0068] After the etching process in step S6 above, as Figure 7 As shown, the above step S7 is performed: texturing is performed on the front side of the pre-cell structure, and passivation layer 70 and anti-reflection layer 80 are formed on the front and back sides of the structure after etching. The passivation layer 70 on the back side of the pre-cell structure covers the P-type doped polysilicon layer 40, the exposed area and the N-type doped polysilicon layer 60.

[0069] Specifically, a texturing process is used to form a textured surface on the front side of the prepared battery structure, and a passivating agent is coated on the textured surface. The battery is then placed in a high-temperature furnace or vacuum evaporation equipment for heat treatment or evaporation, so that the passivating agent reacts with the battery surface to form a dense passivation layer 70. A layer of antireflection film is then coated, and heat treatment or vacuum evaporation is performed again to make the antireflection film and the passivation layer 70 tightly bonded to form a uniform and dense antireflection layer 80. Figure 7 The substrate 10 and the tunnel passivation layer 30 in Figure 3 The description is consistent with that in the text.

[0070] The passivating agent can be selected from any one or more of alumina, boron nitride, and silicates, but is not limited to these types. Those skilled in the art can also rationally select the type of passivating agent according to actual needs. The passivation film can also be formed by direct deposition. The antireflective film can be selected from any one or more of silicon dioxide, alumina, titanium dioxide, and zirconium oxide, but is not limited to these types. Those skilled in the art can also rationally select the material of the antireflective film according to actual needs. The antireflective layer can also be formed by direct deposition. The coating can be selected from any one of solution immersion, sputtering, and ion implantation methods, but is not limited to these methods. Those skilled in the art can also rationally select the coating method according to actual needs.

[0071] In some alternative implementations, such as Figure 4 As shown, the thickness of the exposed P-type doped polysilicon layer 40 is 2 / 5 to 4 / 5 of the thickness of the non-exposed P-type doped polysilicon layer 40. The p-poly can be cleaned by wet etching to ensure that the thickness of the exposed P-type doped polysilicon layer 40 is within the above-mentioned range, thereby providing better doping uniformity and stability during the fabrication process.

[0072] After the texturing process in step S7 above, as follows Figure 8 As shown, the above step S8 is performed: an electrode 90 is formed on the back side of the prepared cell structure. The electrode 90 penetrates the passivation layer 70 and the anti-reflection layer 80 and contacts the P-type doped polycrystalline silicon layer 40 or the N-type doped polycrystalline silicon layer 60 to form a solar cell.

[0073] Specifically, the aforementioned electrode 90 is typically made of a highly conductive metal material such as aluminum or silver, which can effectively draw the photoelectric conversion current out of the solar cell structure, thereby improving the cell's conductivity and efficiency.

[0074] Specifically, at least the passivation layer 70 and the antireflection layer 80 are locally etched to ensure that the electrode 90 can contact the doped layer through the passivation layer 70 and the antireflection layer 80, thereby conducting current. The electrode 90 is fabricated on the back side of the prepared battery structure using a deposition process or magnetron sputtering. The above fabrication process can also employ vacuum evaporation and spraying, but is not limited to these methods. Those skilled in the art can reasonably select the electrode formation method according to actual needs. The conditions for the above heat treatment can include temperature, time, and atmosphere, and those skilled in the art can adjust the heat treatment conditions according to actual needs.

[0075] According to another aspect of this application, a solar cell is provided, such as Figure 8 As shown, the solar cell fabricated by the method described in the above embodiments includes: a pre-cell structure, a passivation layer 70, an anti-reflection layer 80, and an electrode 90. The pre-cell structure includes: a substrate 10, a first composite layer, borosilicate glass 50, and an N-type doped polycrystalline silicon layer 60. The substrate 10 includes a front side and a back side. The first composite layer is located on the back side of the substrate 10 and includes a tunneling passivation layer 30 and a P-type doped polycrystalline silicon layer 40. The P-type doped polycrystalline silicon layer 40 is located opposite the tunneling passivation layer 30 to the substrate. On a portion of the surface of substrate 10, borosilicate glass 50 is located on the side of P-type doped polycrystalline silicon layer 40 facing away from substrate 10, and N-type doped polycrystalline silicon layer 60 is located on the portion of the surface of tunneling passivation layer 30 facing away from substrate 10; passivation layer 70 is located on the front and back sides of the pre-cell structure, with the passivation layer 70 on the back side covering P-type doped polycrystalline silicon layer 40, a portion of substrate 10, and N-type doped polycrystalline silicon layer 60; antireflection layer 80 is located on the front and back sides of the pre-cell structure, and antireflection layer 80 covers passivation layer 70. Electrode 90 penetrates passivation layer 70 and antireflection layer 80 to contact P-type doped polycrystalline silicon layer 40 or N-type doped polycrystalline silicon layer 60 to form a solar cell.

[0076] The solar cells prepared by the above-described method have N-type doped polycrystalline silicon layers and P-type doped polycrystalline silicon layers located in the same layer, which reduces the overall thickness of the solar cells. Furthermore, the preparation is achieved through a single inversion process, which simplifies the process flow, reduces production costs, and increases production capacity.

[0077] In the above optional embodiments, the substrate can serve to support and stabilize the pre-cell structure, the P-type doped polycrystalline silicon layer and the N-type doped polycrystalline silicon layer serve to perform photoelectric conversion, the borosilicate glass provides protection, the tunneling passivation layer can improve the photoelectric conversion efficiency, the passivation layer can improve the passivation effect of the cell, and the antireflection layer can improve the light absorption rate and conversion efficiency of the solar cell.

[0078] In some optional embodiments, the thickness of the tunneling passivation layer is 1.3 nm to 2.5 nm, the thickness of the P-type doped polycrystalline silicon layer is 100 nm to 400 nm, and the thickness of the N-type doped polycrystalline silicon layer is 40 nm to 320 nm. The thickness of the tunneling passivation layer, being 1.3 nm to 2.5 nm, can effectively reduce the surface recombination rate and decrease surface recombination loss. When depositing the P-type doped polycrystalline silicon layer on the tunneling passivation layer, its thickness is controlled between 100 nm and 400 nm; when depositing the N-type doped polycrystalline silicon layer on the P-type doped polycrystalline silicon layer, its thickness is controlled between 40 nm and 320 nm, thereby controlling the structure and material thickness of the solar cell.

[0079] In some alternative embodiments, the thickness of the N-type doped polysilicon layer is 2 / 5 to 4 / 5 of the thickness of the P-type doped polysilicon layer.

[0080] In the above optional embodiments, the thickness ratio of N-type and P-type polycrystalline silicon layers is adjusted by controlling parameters such as doping concentration, intensity, and doping time, so as to precisely control the fabrication process parameters and achieve the required ratio of N-type doped polycrystalline silicon layers and P-type doped polycrystalline silicon layers.

[0081] In some alternative implementations, the doping concentration of the N-type doped polysilicon layer is 2E20cm⁻¹. -3 ~1E21cm -3 .

[0082] In the above optional embodiments, N-type doping can introduce additional free electrons, increase the conductivity of the material, facilitate electron migration and reduce electron-hole recombination, and enable the doping concentration of the N-type material to reach 2E20cm during the doping process. -3 ~1E21cm -3 The range.

[0083] According to another aspect of this application, a photovoltaic module is provided, comprising at least one solar cell.

[0084] In the above optional embodiments, the photovoltaic module can be formed by combining multiple solar cells together and connecting them into an integrated system, so as to convert solar energy into electrical energy.

[0085] The technical solutions of this application can be used for all-back contact cells with gridless technology (0BB, Zero Busbar) or multi-busbar technology (MBB), all-back contact cells (IBC, Interdigitated Back Contact), all-back contact solar cells (ABC, All Back Contact), hybrid passivated back contact cells (HPBC), TOPcon-IBC cells, and tandem cells (composed of perovskite cells and BC cells).

[0086] The method for preparing the solar cell described above in this application will be specifically described below with reference to specific embodiments.

[0087] Example 1

[0088] This embodiment provides a method for preparing a solar cell, including the following steps:

[0089] 1. Provide a substrate having a front side and a back side, wherein the substrate material is silicon and the thickness is 200nm;

[0090] 2. A first composite layer is formed on the back side, the first composite layer including a tunneling passivation layer and a P-type doped polysilicon layer, wherein the thickness of the tunneling oxide layer is 1.9 nm and the thickness of the P-type doped polysilicon layer is 250 nm.

[0091] 3. A borosilicate glass is formed on the side of the first composite layer away from the substrate, and the thickness of the borosilicate glass is 95 nm.

[0092] 4. Laser etching is used to remove part of the borosilicate glass, and wet cleaning process is used to remove part of the P-type doped polysilicon layer, so that part of the P-type doped polysilicon layer is exposed. The thickness of the P-type doped polysilicon after wet etching is 2 / 5 of the thickness of the P-type doped polysilicon before cleaning.

[0093] 5. The exposed P-type doped polycrystalline silicon layer is doped to form an N-type doped polycrystalline silicon layer, thus forming the preliminary cell structure. The doping concentration of the N-type doped polycrystalline silicon layer is 2E20cm⁻¹. -3 .

[0094] 6. The back side of some of the pre-built cell structures is etched to separate the N-type doped polysilicon layer from the P-type doped polysilicon layer, and the back side of the substrate has an exposed area.

[0095] 7. The front side of the pre-cell structure is texturized, and a passivation layer and an anti-reflection layer are formed on the front and back sides of the structure after etching. The passivation layer on the back side of the pre-cell structure covers the P-type doped polysilicon layer, the exposed area and the N-type doped polysilicon layer.

[0096] 8. An electrode is formed on the back side of the prepared cell structure. The electrode penetrates the passivation layer and the antireflection layer and contacts the P-type doped polycrystalline silicon layer or the N-type doped polycrystalline silicon layer to form a solar cell.

[0097] Comparative Example 1

[0098] A method for preparing a solar cell is provided, comprising the following steps:

[0099] 1. Provide a substrate having a front side and a back side, wherein the substrate material is silicon and the thickness is 200nm;

[0100] 2. A tunneling passivation layer and a P-type doped polysilicon layer are formed on the back side using a deposition process. The surface of the P-type doped polysilicon layer has borosilicate glass. The thickness of the tunneling oxide layer is 1.9 nm, the thickness of the P-type doped polysilicon layer is 250 nm, and the thickness of the borosilicate glass is 95 nm.

[0101] 3. Laser-cut the entire borosilicate glass layer to expose the P-type doped polycrystalline silicon layer, and then use a wet cleaning process to remove part of the P-type doped polycrystalline silicon layer to expose the substrate.

[0102] 4. An N-type doped polysilicon layer is deposited on the P-type doped polysilicon layer, covering the exposed area of ​​the substrate. The total thickness of the P-type and N-type doped polysilicon layers is 300 nm, with the N-type doped polysilicon layer having a doping concentration of 2E20 cm⁻¹. -3 ;

[0103] 5. The N-type doped polysilicon layer on the P-type doped polysilicon layer is removed by a wet cleaning process, and the P-type doped polysilicon layer is laser-etched to separate the P-type doped polysilicon layer and the N-type doped polysilicon layer, forming a preliminary cell structure.

[0104] 6. The front side of the pre-cell structure is texturized, and a passivation layer and an anti-reflection layer are formed on the front and back sides of the structure after etching. The passivation layer on the back side of the pre-cell structure covers the P-type doped polysilicon layer, the exposed area, and the N-type doped polysilicon layer.

[0105] 7. An electrode is formed on the back side of the prepared cell structure. The electrode penetrates the passivation layer and the antireflection layer and contacts the P-type doped polycrystalline silicon layer or the N-type doped polycrystalline silicon layer to form a solar cell.

[0106] The performance of the solar cells obtained using the methods described in Example 1 and Comparative Example 1 was tested, and the results are as follows:

[0107] Table 1

[0108]

[0109] As can be seen from the data of Example 1 and Comparative Example 1 in the table above, after n-poly and p-poly are prepared by a single preparation process in Example 1, the battery maintains a relatively thin thickness throughout the preparation process, and the area of ​​laser-opened film is very small, which significantly reduces the warpage of the battery, minimizes laser damage, and significantly improves photoelectric conversion efficiency, open circuit voltage, and fill factor.

[0110] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0111] 1) The solar cell fabrication method described in the embodiments of this application, based on the traditional TBC cell manufacturing, involves local laser delamination and wet cleaning to remove BSG, exposing the underlying p-poly. The BSG in the un-laser-delaminated area serves as a phosphorus-doped barrier layer, while the exposed area is heavily doped with phosphorus to compensate for doping inversion and form an n-poly structure. The n-poly structure formed by compensating for inversion has the same passivation contact performance as the structure prepared by conventional processes, without affecting the final quality of the n-poly region of the cell. The above structure eliminates the secondary poly deposition step, simplifies the process flow, reduces the overall poly layer thickness, increases production capacity, reduces manufacturing costs, and reduces silicon wafer stress deformation. At the same time, it reduces the laser delamination area, reduces laser damage, improves cell efficiency, and increases laser production capacity.

[0112] 2) The solar cell preparation method described in the embodiments of this application is compatible with the production line and does not require additional equipment or special gases. It is easy to manufacture. The laser is used for local film opening, which eliminates the complex patterning process (such as ink printing). The wet method uses conventional cleaning processes, which eliminates the pollution from cleaning organic substances such as ink.

[0113] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0114] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for preparing a solar cell, characterized in that, include: A substrate is provided, the substrate having a front side and a back side; A first composite layer is formed on the back side, the first composite layer comprising a tunneling passivation layer and a P-type doped polysilicon layer; Borosilicate glass is formed on the side of the first composite layer that is away from the substrate; Remove part of the borosilicate glass and part of the P-type doped polysilicon layer, so that part of the P-type doped polysilicon layer is exposed; The exposed P-type doped polycrystalline silicon layer is doped to form an N-type doped polycrystalline silicon layer, thus forming a preliminary cell structure; The back side of a portion of the prepared cell structure is etched to separate the N-type doped polysilicon layer from the P-type doped polysilicon layer, and the back side of the substrate has an exposed area. The front side of the pre-cell structure is texturized, and a passivation layer and an anti-reflection layer are formed on the front and back sides of the structure after the etching process. The passivation layer on the back side of the pre-cell structure covers the P-type doped polysilicon layer, the exposed area, and the N-type doped polysilicon layer. An electrode is formed on the back side of the pre-cell structure. The electrode penetrates the passivation layer and the anti-reflection layer and contacts the P-type doped polycrystalline silicon layer or the N-type doped polycrystalline silicon layer to form the solar cell.

2. The preparation method according to claim 1, characterized in that, During the formation of the pre-cell structure, and after the formation of the N-type doped polycrystalline silicon layer, the fabrication method further includes: Phosphosilicate glass is formed on the side of the N-type doped polycrystalline silicon layer away from the substrate.

3. The preparation method according to claim 1, characterized in that, The steps for forming the first composite layer include: The tunneling passivation layer and the P-type doped polysilicon layer are alternately formed on the back side of the substrate.

4. The preparation method according to claim 3, characterized in that, The steps for forming the N-type doped polysilicon layer include: The first composite layer is doped to form alternating tunneling passivation layers and N-type doped polysilicon layers.

5. The preparation method according to claim 2, characterized in that, Before the step of forming a passivation layer and an antireflection layer on the front and back sides of the pre-cell structure after the etching process, the fabrication method further includes: Remove the borosilicate glass and the phosphosilicate glass.

6. The preparation method according to claim 2, characterized in that, The thickness of the exposed P-type doped polysilicon layer is 2 / 5 to 4 / 5 of the thickness of the unexposed P-type doped polysilicon layer.

7. A solar cell, characterized in that, The solar cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 6, and the solar cell comprises: The preliminary cell structure includes: a substrate, a first composite layer, borosilicate glass, and an N-type doped polycrystalline silicon layer, wherein: The substrate includes a front side and a back side. The first composite layer is located on the back side of the substrate. The first composite layer includes a tunneling passivation layer and a P-type doped polysilicon layer. The P-type doped polysilicon layer is located on a portion of the surface of the tunneling passivation layer facing away from the substrate. The borosilicate glass is located on the side of the P-type doped polysilicon layer facing away from the substrate. The N-type doped polysilicon layer is located on a portion of the surface of the tunneling passivation layer facing away from the substrate. A passivation layer is located on the front and back sides of the pre-cell structure, and the passivation layer on the back side covers the P-type doped polysilicon layer, part of the substrate and the N-type doped polysilicon layer; An anti-reflection layer is located on the front and back sides of the pre-cell structure, and the anti-reflection layer covers the passivation layer; An electrode is located on the back side of the pre-cell structure. The electrode penetrates the passivation layer and the anti-reflection layer and contacts the P-type doped polycrystalline silicon layer or the N-type doped polycrystalline silicon layer to form the solar cell.

8. The solar cell according to claim 7, characterized in that, The thickness of the N-type doped polycrystalline silicon layer is 2 / 5 to 4 / 5 of the thickness of the P-type doped polycrystalline silicon layer.

9. The solar cell according to claim 7, characterized in that, The doping concentration of the N-type doped polysilicon layer is 2E20cm⁻¹. -3 ~1E21cm -3 .

10. A photovoltaic module, characterized in that, It includes at least one solar cell according to any one of claims 7 to 9.

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